A magnetic tunnel junction is an integrated circuit component having two magnetic materials separated by a thin non-magnetic dielectric material. The dielectric material is sufficiently thin such that electrons can tunnel from one magnetic material to the other through the dielectric material under appropriate conditions. At least one of the magnetic materials is ferromagnetic whereby its magnetic domain direction can be switched between two states, and is commonly referred to as the “free” or “recording” material. The other material may not be ferromagnetic, and may commonly be referred to as the “reference” or “fixed” material. The reference material and the recording material are electrically coupled to respective conductive nodes. The resistance of current flow between those two nodes through the reference material, dielectric material, and recording material is dependent upon the magnetic domain direction of the recording material relative to that of the reference material. Accordingly, a magnetic tunnel junction can be programmed into one of at least two states, and those states can be sensed by measuring current flow through the magnetic tunnel junction. Since magnetic tunnel junctions can be “programmed” between two current-conducting states, they have been proposed for use in memory integrated circuitry. Additionally, magnetic tunnel junctions may be used in logic or other circuitry apart from or in addition to memory.
The magnetic domain direction of the recording material can be switched by an external magnetic field or by using a spin-polarized current to result in a spin-transfer torque effect. Charge carriers (such as electrons) have a property known as “spin” which is a small quantity of angular momentum intrinsic to the carrier. An electric current is generally unpolarized (having 50% “spin-up” and 50% “spin-down” electrons). A spin-polarized current is one with more electrons of either spin. By passing a current through magnetic material, one can produce a spin-polarized current. If a spin-polarized current is directed into a ferromagnetic material, angular momentum can be transferred to that material, thereby affecting its orientation. This can be used to excite oscillations or even flip (i.e., switch) the orientation/domain direction of the ferromagnetic material.
Typical existing proposals for magnetic tunnel junctions form the two magnetic materials and non-magnetic material as a pillar, for example that may have circular or rectangular horizontal cross-section. Those configurations are typically created by depositing a stack of the three materials, followed by etching the stack to form a plurality of magnetic tunnel junctions which individually include the three materials. Unfortunately, etching of such materials can cause damage to the sidewalls/edges of the resultant pillars. This damage can be sufficient to adversely affect device operation, particularly as the pillars become smaller and narrower.